Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 212023

Area Forecast Discussion
National Weather Service Lincoln IL
323 PM CDT Wed Mar 21 2018

.SHORT TERM...(This evening through Thursday)
ISSUED AT 323 PM CDT Wed Mar 21 2018

High pressure moving into central and southeast Illinois tonight
will give us a clear and unseasonably cold night. Lows from 25 to
30 can be expected across the whole forecast area.

Increasing mid level warm advection during the day Thursday will
result in increasing clouds across central IL during the morning,
and in eastern and southeast IL early in the afternoon. There
should be enough isentropic lifting for some light rain in west
central and parts of central Illinois from the afternoon into
early evening. However, any precipitation that forms will be
fighting quite a bit of dry air aloft, so amounts should be very


.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 323 PM CDT Wed Mar 21 2018

A very active, wet period is anticipated across the entire
forecast area from later Friday through Saturday, and again from
late Monday through Wednesday. The models are in remarkably good
agreement through much of the time period, with liquid
precipitation amounts expected to total 3.00 to 4.00 inches across
central IL and 2.00 to 3.00 inches in southeast IL. Area rivers
have just dropped below flood stage in most areas, so we will need
to keep an eye on rising levels and the potential for renewed
flooding by the middle of next week.

The first challenge will be with precipitation amounts and
precipitation type for late Friday into Saturday. Isentropic lift
rapidly increases by Friday afternoon and continues into Saturday
with an approaching low pressure system from Kansas into southern
IL by 18z Saturday. Plenty of low level moisture is expected to be
available with impressive mixing ratios and precipitable water
around or greater than 1.00 inch. Low level temperature fields
will be tricky along and north of I-74 where a mix with and
eventual change over to snow is expected, particularly later in
the day Saturday as the low moves to the ESE, allowing colder air
to filter in. At this time, it appears the best forcing and
temperature fields conducive for snow will be up toward the I-80
corridor. However, some parts of the northern forecast area from
Lacon to northern McLean County and north of Champaign and
Danville could see a few inches of snow by Saturday evening.

The rest of the forecast area in central and southeast IL can
expect an extended period of rain Friday evening through Saturday.
The available lift and aforementioned moisture could result in a
few thunderstorms as well, so the mention of isolated thunder will
be added, especially south of I-72.

Another potent low pressure system is expected to approach central
Illinois for Tuesday and Wednesday. Again, the models are in
pretty good agreement that ample moisture will bring even higher
rainfall totals to central and southeast IL, with 1.50 to 2.50
inches of rain possible. Could also be a few t-storms as the low
and front approach Wednesday, but hold off on mentioning those for
now until the timing of the system is better established.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1240 PM CDT Wed Mar 21 2018

VFR conditions can be expected during the entire 24 hour TAF
period. The only concern will be low level winds in eastern IL
this afternoon. The gradient between low pressure off of the mid-
Atlantic coast and high pressure in the southern Plains will
produce brisk N-NNW winds, particularly east of I-57. There may be
a gust up to 20-22kts at times, but not often enough to include
in the KCMI TAF.

The high pressure ridge axis will move into central IL by daybreak
Thursday. This will result in a rapid diminishing of the wind
early this evening, which is expected to continue through Thursday




LONG TERM...Miller
AVIATION...Miller is the U.S. government's official web portal to all federal, state and local government web resources and services.